1. Technical Field
The present disclosure relates generally to a surgical instrument for injecting a fluid into tissue and, more particularly to a surgical instrument for injecting an imaging radio label material into breast tissue for the detection of breast carcinoma.
2. Background of Related Art
Breast carcinoma is the most common cancer and the second leading cause of cancer-related death in women living in the United States. The incidence of breast cancer is increasing by about three percent per year. Recent studies show that one in eight women in the United States will develop breast cancer. Early detection lowers mortality and prolongs life expectancy of those having breast cancer.
Presently, standard screening tests for early detection of breast cancer include breast self-examination, breast examination by a physician, and mammography. In general, physical examination alone will detect, at best, only sixty to eighty percent of breast masses, whereas mammography will detect eighty to ninety percent of breast masses in women not having dense breasts. In women having dense breasts, mammography has a false-negative rate of twenty-five to forty-five percent, and has a positive predictive value of only thirty percent. Only one in every four to six biopsies performed to confirm or rule out malignancy of suspicious lesions detected during mammograms will be malignant. Thus, the majority of biopsies prove to be unnecessary, i.e., the lesion is benign. Considering that the economic cost as well as the physical and psychological stress of undergoing a biopsy is high, the need for a noninvasive and accurate technique to better discriminate between benign and malignant mammographic abnormalities which require biopsy is clearly present.
One such technique being developed for noninvasively and accurately discriminating between malignant and benign mammographic abnormalities is Lymphatic Breast Mapping (xe2x80x9cLBMxe2x80x9d). During an LBM procedure, a quantity of radioactive tracer or dye is injected into and around a tumor. Because of the tracer""s biochemistry, the tumor will collect more of the tracer than does normal healthy tissue. Thus, when the radioactive tracer decays and emits gamma rays, a higher number of these gamma rays will originate from tumor sites than from equal volumes of healthy tissue. The tracer distribution and gamma ray emission can be identified using a scintillation camera to enable doctors to identify the presence or absence of cancer.
Accordingly, a need exists for a surgical instrument for injecting a radioactive tracer into body tissue at precise locations adjacent a tumor.
In accordance with the present disclosure, a tissue mapping injection device is disclosed that is capable of injecting an imaging radio label material or dye into the body at a location encompassing target tissue. The injection device includes a housing, an elongated body portion coupled to and extending distally from the housing, an actuator assembly slidably supported within the housing from a retracted to an advanced position, and at least one needle coupled to the distal end of the actuator assembly. The actuator assembly includes a plunger which is slidably positioned along a cylindrical bore formed within the housing. An engagement member is coupled to or monolithically formed with the plunger and is positioned to be engaged by the thumb of a surgeon. The plunger has a first end which extends distally from one end of the housing in a direction opposite to the elongated body portion. The plunger defines a fluid delivery channel and includes a distal end adapted to receive a fluid delivery hose.
A connector rod is coupled to and extends from the plunger through the elongated body portion. The connector rod also defines a fluid delivery channel which communicates with the plunger delivery channel. The needles are connected to the distal end of the connector rod and are formed from a shape memory material. Each of the needles defines an injection delivery channel which communicates with the fluid delivery channel of the connector rod. In a relaxed state, the needles curve outwardly at a predetermined angle relative to the longitudinal axis of the elongated body portion. In one embodiment, four needles are secured to the distal end of the connector rod. Each of the needles is substantially identically shaped in its relaxed state.
In use, when the plunger is in the retracted position, the needles are positioned within elongated body portion and are deformed by the body portion to a substantially straight configuration. When the plunger is moved to the advanced position, the needles are moved distally out of the distal end of the elongated body portion. The needles are no longer deformed by the elongated body portion and thus, return to the relaxed state curving outwardly from the longitudinal axis of the body portion. Since each of the needles is similarly shaped, the tips of the needles lie in a common plane and extend into four quadrants surrounding a target tissue. Each of the needles is spaced approximately 90xc2x0 from adjacent needles. Fluid can be injected into the tissue surrounding the target tissue via the delivery channels in the plunger and the injection channel formed in the needles.
In an alternate embodiment, eight needles are secured to the distal end of the connector rod. The eight needles form two sets of four needles, wherein each needle has a substantially identical configuration in the relaxed state as the other needles in that set of needles. When the needles are advanced out of the distal end of the elongated body portion, the tips of the first set of needles lie in a first plane and the tips of the second set of needles lie in a second plane spaced from the first plane. Each of the needles of each set of needles extends into one of the four quadrants surrounding a target tissue and is spaced approximately ninety degrees from adjacent needles.